Some applications require an original document to be preserved and require modifications to be stored in new versions. In IBM® Content Manager, you can keep multiple versions of items and objects.
If you set the version policy to allow multiple versions, you can set a maximum number of versions or allow an unlimited number. If you set a maximum number, when the specified maximum is reached, the oldest version is deleted and the most recent version is saved.
If the item type that you are creating is classified as a resource item or document part, the version policy applies also to the object on the resource manager.
If the item type that you are creating is a document, you can specify supplemental version policy information for the specific document parts. You specify this information in the Define Document Management Relations window, which you reach from the Document Management page. The version policies are independent of each other and can be enabled separately.
The version policy for document parts supplements the version policy that you set on the Definition page. For example, on the Definition page, you might allow a maximum of three multiple versions. In the Define Document Management Relations window, you might specify Never create for the base part, but Always create for the notelog and annotation parts. In this case, one version of the base part and up to three versions each of the notelog and annotation parts can exist at any given time.
In the document model, versioning is specified at the document level and at the part level. If versioning for both the document and part are on, and if you create a new version of the part, a new version of the document is created. If parts are merely replaced (no new version of the part is created) and attributes are not changed, a new version of the document is not created.
The conversion of an existing item type from the Never create version policy to Always create or Prompt to create will be rejected if the item type has unique attributes, or if it has created a unique component index on one or more attributes. The reason is that during the conversion, IBM Content Manager checks the component tables for unique indexes that are already defined with user attributes. These indexes consist only of columns that correspond to the user attributes.
If such an index is found, the operation is rejected because item types that are enabled for versioning cannot have unique indexes on their attributes. When a new version create or update operation is attempted, a unique index causes failure because the new version will have the same value of the attributes. This problem causes a database duplicate index error.
In this case, an error message advises users to remove the unique index or indexes manually by using the system administration client or the database tool before trying the operation again.